| Internet App | Location App |
|---|---|
 |
 |
- Architecture Overview
- Project Structure
- Technology Stack
- Inter-App Communication Strategy
- Security Implementation
┌─────────────────┐ Commands/Queries ┌─────────────────┐
│ Internet App │ ────────────────────────────────> │ Location App │
│ (MVI/Koin) │ │ (MVVM/Hilt) │
│ │ <──────────────────────────────── │ │
└─────────────────┘ Responses/Updates └─────────────────┘
│ │
│ │
▼ ▼
UI State Display Background Location Service
+ Encrypted Data Storage
Internet App (MVI + Koin):
- Sends commands to Location App (start/stop service, retrieve locations)
- Receives and displays responses
- Implements MVI architecture for predictable state management
- Provides compose UI for all operations
Location App (MVVM + Hilt):
- Collects user location every 2-3 minute in the background
- Stores location data with AES-256-GCM encryption using Android KeyStore
- Provides secure ContentProvider interface for external commands
- Auto-restarts after process termination
- Displays collected locations in a compose UI
AndroidcodeChallengeInterApp/
├── .github/
│ └── workflows/
│ └── ci.yml
│
├── config/
│ └── detekt/
│ └── detekt.yml
│
├── internet-app/
│ ├── app/
│ │ ├── src/main/
│ │ │ ├── kotlin/dev/internetapp/
│ │ │ │ └── InternetApp.kt
│ │ │ ├── AndroidManifest.xml
│ │ │ └── res/
│ │ └── src/androidTest/
│ │ └── java/dev/internetapp/presentation/
│ │ └── InterAppCommunicationTest.kt
│ │
│ ├── core/
│ │ └── common/
│ │ └── src/main/kotlin/dev/internetapp/core/common/di/
│ │ └── CommonModule.kt
│ │
│ └── feature/
│ ├── command-sender/
│ │ ├── src/main/kotlin/dev/internetapp/feature/commandsender/
│ │ │ ├── data/repository/
│ │ │ │ └── CommandRepositoryImpl.kt
│ │ │ ├── domain/
│ │ │ │ ├── repository/
│ │ │ │ │ └── CommandRepository.kt
│ │ │ │ └── usecase/
│ │ │ │ ├── GetAllLocationsUseCase.kt
│ │ │ │ ├── GetLatestLocationUseCase.kt
│ │ │ │ ├── StartServiceUseCase.kt
│ │ │ │ └── StopServiceUseCase.kt
│ │ │ └── di/
│ │ │ └── CommandSenderModule.kt
│ │ └── build.gradle.kts
│ │
│ └── response-display/
│ ├── src/main/kotlin/dev/internetapp/feature/responsedisplay/
│ │ ├── domain/model/
│ │ │ ├── CommandEffect.kt
│ │ │ ├── CommandIntent.kt
│ │ │ ├── CommandUiState.kt
│ │ │ └── ServiceStatus.kt
│ │ ├── presentation/
│ │ │ ├── components/
│ │ │ │ ├── ControlButtons.kt
│ │ │ │ ├── InfoCards.kt
│ │ │ │ ├── LocationsList.kt
│ │ │ │ ├── ResponseCards.kt
│ │ │ │ └── ServiceStatusCard.kt
│ │ │ ├── di/
│ │ │ │ └── ResponseDisplayModule.kt
│ │ │ ├── ui/theme/
│ │ │ │ └── Theme.kt
│ │ │ ├── viewmodel/
│ │ │ │ └── CommandViewModel.kt
│ │ │ └── MainActivity.kt
│ ├── src/test/kotlin/
│ │ └── dev/internetapp/feature/responsedisplay/
│ │ └── CommandViewModelTest.kt
│ └── build.gradle.kts
│
│
├── location-app/
│ ├── app/
│ │ ├── src/main/
│ │ │ ├── kotlin/dev/locationapp/
│ │ │ │ └── LocationApp.kt
│ │ │ ├── AndroidManifest.xml
│ │ │ └── res/
│ │ └── build.gradle.kts
│ │
│ ├── core/
│ │ ├── common/
│ │ │ ├── src/main/kotlin/dev/locationapp/di/
│ │ │ │ └── AppModule.kt
│ │ │ └── build.gradle.kts
│ │ │
│ │ ├── database/
│ │ │ ├── src/main/kotlin/dev/locationapp/di/
│ │ │ │ └── DatabaseModule.kt
│ │ │ └── build.gradle.kts
│ │ │
│ │ └── security/
│ │ ├── src/main/kotlin/dev/locationapp/core/security/
│ │ │ ├── data/
│ │ │ │ └── CryptoManager.kt
│ │ │ ├── di/
│ │ │ │ └── SecurityModule.kt
│ │ │ └── domain/
│ │ │ ├── EncryptedData.kt
│ │ │ └── ICryptoManager.kt
│ │ ├── src/test/kotlin/
│ │ │ └── dev/locationapp/core/security/
│ │ │ ├── data/
│ │ │ │ └── CryptoManagerTest.kt
│ │ │ └── domain/
│ │ │ └── FakeCryptoManager.kt
│ │ └── build.gradle.kts
│ │
│ └── feature/
│ ├── command/
│ │ ├── src/main/
│ │ │ ├── kotlin/dev/locationapp/feature/command/
│ │ │ │ ├── data/handler/
│ │ │ │ │ └── CommandHandlers.kt
│ │ │ │ ├── presentation/provider/
│ │ │ │ │ └── LocationCommandProvider.kt
│ │ │ │ └── di/
│ │ │ │ └── CommandFeatureModule.kt
│ │ │ ├── AndroidManifest.xml
│ │ │ └── res/
│ │ └── build.gradle.kts
│ │
│ └── location/
│ ├── src/main/
│ │ ├── kotlin/dev/locationapp/feature/location/
│ │ │ ├── data/
│ │ │ │ ├── local/
│ │ │ │ │ ├── LocationDao.kt
│ │ │ │ │ ├── LocationDatabase.kt
│ │ │ │ │ └── LocationEntity.kt
│ │ │ │ └── repository/
│ │ │ │ └── LocationRepositoryImpl.kt
│ │ │ ├── domain/
│ │ │ │ ├── repository/
│ │ │ │ │ └── LocationRepository.kt
│ │ │ │ └── usecase/
│ │ │ │ ├── GetAllLocationsUseCase.kt
│ │ │ │ ├── GetLatestLocationUseCase.kt
│ │ │ │ └── SaveLocationUseCase.kt
│ │ │ ├── presentation/
│ │ │ │ ├── components/
│ │ │ │ │ └── LocationScreenComponents.kt
│ │ │ │ ├── ui/theme/
│ │ │ │ │ └── Theme.kt
│ │ │ │ ├── LocationListState.kt
│ │ │ │ ├── LocationListViewModel.kt
│ │ │ │ └── MainActivity.kt
│ │ │ ├── service/
│ │ │ │ ├── BootReceiver.kt
│ │ │ │ └── LocationCollectionService.kt
│ │ │ └── di/
│ │ │ └── LocationFeatureModule.kt
│ │ └── AndroidManifest.xml
│ ├── src/test/kotlin/
│ │ └── dev/locationapp/feature/location/
│ │ ├── data/repository/
│ │ │ └── LocationRepositoryImplTest.kt
│ │ ├── di/
│ │ │ └── TestDatabaseModule.kt
│ │ └── service/
│ │ └── LocationCollectionServiceTest.kt
│ └── build.gradle.kts
│
├── shared/
│ ├── debug/
│ │ ├── src/main/
│ │ │ ├── kotlin/dev/shared/debug/
│ │ │ │ ├── presentation/
│ │ │ │ │ ├── components/
│ │ │ │ │ │ ├── EventsTab.kt
│ │ │ │ │ │ ├── ExportDialog.kt
│ │ │ │ │ │ ├── MetricsTab.kt
│ │ │ │ │ │ └── SummaryTab.kt
│ │ │ │ │ └── DebugActivity.kt
│ │ │ │ └── ui/theme/
│ │ │ │ └── DebugTheme.kt
│ │ │ └── res/
│ │ └── build.gradle.kts
│ │
│ └── protocol/
│ ├── src/main/
│ │ ├── kotlin/dev/abbasian/protocol/
│ │ │ ├── analytics/
│ │ │ │ ├── AnalyticsEvent.kt
│ │ │ │ └── PerformanceMetric.kt
│ │ │ ├── data/
│ │ │ │ ├── analytics/
│ │ │ │ │ ├── AnalyticsLogger.kt
│ │ │ │ │ └── MockAnalyticsService.kt
│ │ │ │ └── constants/
│ │ │ │ └── ProtocolConstants.kt
│ │ │ └── domain/
│ │ │ ├── analytics/
│ │ │ │ └── IAnalyticsService.kt
│ │ │ ├── logger/
│ │ │ │ └── AppLogger.kt
│ │ │ └── model/
│ │ │ ├── CommandResult.kt
│ │ │ ├── LocationCommand.kt
│ │ │ ├── LocationData.kt
│ │ │ └── LocationResponse.kt
│ │ └── res/
│ └── build.gradle.kts
│
├── settings.gradle.kts
└── README.md
- Language: Kotlin
- DI: Koin
- Architecture: MVI + Clean Architecture
- Async: Coroutines + Flow
- State Management: StateFlow + sealed classes
- Communication: ContentProvider or Messenger Service
- Language: Kotlin
- DI: Hilt
- Architecture: MVVM + Clean Architecture
- Async: Coroutines + Flow
- Database: Room with SQLCipher
- Background: WorkManager + Foreground Service
- Location: FusedLocationProviderClient
- Security: Android KeyStore + AES-256-GCM
- Logger: Timber with custom tree
- Protocol: Sealed classes for commands/responses
Why did I choose this implementation?
- ✅ Secure - Can restrict access via permissions
- ✅ Reliable - System-managed lifecycle
- ✅ Bidirectional - Supports both queries and callbacks
- ✅ Testable - Can mock ContentResolver
- ✅ Battery-efficient - No persistent connections
// command Types in shared protocol
sealed class LocationCommand {
object StartService : LocationCommand()
object StopService : LocationCommand()
object GetAllLocations : LocationCommand()
object GetLatestLocation : LocationCommand()
}
sealed class LocationResponse {
data class Success(val message: String) : LocationResponse()
data class LocationList(val locations: List<LocationData>) : LocationResponse()
data class SingleLocation(val location: LocationData?) : LocationResponse()
data class Error(val message: String, val code: ErrorCode) : LocationResponse()
}Location App - Provider:
class LocationCommandProvider : ContentProvider() {
override fun call(method: String, arg: String?, extras: Bundle?): Bundle? {
// for call commands and return encrypted responses
}
}Internet App - Client:
class CommandRepositoryImpl(): CommandRepository {
private val contentResolver: ContentResolver = context.contentResolver
override suspend fun sendCommand(command: LocationCommand): LocationResponse {
// send command via contentResolver.call()
}
}class CryptoManager @Inject constructor() {
private val keyStore =
KeyStore.getInstance(KEYSTORE_PROVIDER).apply {
load(null)
}
private fun getOrCreateKey(): SecretKey {
if (!keyStore.containsAlias(KEY_ALIAS)) {
createKey()
}
return keyStore.getKey(KEY_ALIAS, null) as SecretKey
}
override fun encrypt(plainText: String): EncryptedData {
val cipher = Cipher.getInstance(TRANSFORMATION)
cipher.init(Cipher.ENCRYPT_MODE, getOrCreateKey())
val iv = cipher.iv
val encrypted = cipher.doFinal(plainText.toByteArray(Charsets.UTF_8))
return EncryptedData(encrypted, iv)
}
override fun decrypt(encryptedData: EncryptedData): String {
val cipher = Cipher.getInstance(TRANSFORMATION)
val spec = GCMParameterSpec(GCM_TAG_LENGTH, encryptedData.iv)
cipher.init(Cipher.DECRYPT_MODE, getOrCreateKey(), spec)
val decrypted = cipher.doFinal(encryptedData.data)
return String(decrypted, Charsets.UTF_8)
}
companion object {
private const val KEYSTORE_PROVIDER = "AndroidKeyStore"
private const val TRANSFORMATION = "AES/GCM/NoPadding"
}
}<provider
android:name="dev.locationapp.feature.command.presentation.provider.LocationCommandProvider"
android:authorities="dev.locationapp.provider"
android:enabled="true"
android:exported="true"
android:grantUriPermissions="true"
android:permission="dev.locationapp.permission.ACCESS_LOCATION_COMMANDS"
android:readPermission="dev.locationapp.permission.ACCESS_LOCATION_COMMANDS"
android:writePermission="dev.locationapp.permission.ACCESS_LOCATION_COMMANDS"
android:multiprocess="false" />
<permission
android:name="dev.locationapp.permission.ACCESS_LOCATION_COMMANDS"
android:protectionLevel="signature"
android:description="@string/permission_description"
android:label="@string/permission_label" />class InterAppCommunicationTest {
@Test
fun `sendStartServiceCommandAndReceiveSuccessResponse`()
@Test
fun `sendGetLocationsCommandReturnsLocationList`()
}
class CommandViewModelTest {
@Test
fun `start service intent updates state to running`()
@Test
fun `stop service intent updates state to stopped`()
@Test
fun `get all locations intent updates locations list`()
@Test
fun `error response updates error state`()
@Test
fun `effect emits success on start service`()
}class LocationRepositoryImplTest {
@Test
fun `saveLocation encrypts and stores location`()
@Test
fun `getAllLocations decrypts and returns locations`()
@Test
fun `getLatestLocation returns null when no data`()
}
@HiltAndroidTest
class LocationCollectionServiceTest {
@Test
fun `service starts successfully`()
@Test
fun `onCreate creates notification channel`()
@Test
fun `onStartCommand with no action starts collection`()
@Test
fun `onStartCommand with ACTION_START_COLLECTION starts collection`()
@Test
fun `onStartCommand with ACTION_STOP_COLLECTION stops collection`()
@Test
fun `stopLocationCollection stops service`()
@Test
fun `onBind returns null`()
@Test
fun `service without location permission stops itself`()
@Test
fun `service lifecycle completes successfully`()
@Test
fun `onDestroy cleans up resources`()
@Test
fun `starting collection twice logs warning`()
@Test
fun `stopping collection when not running logs warning`()
@Test
fun `notification has correct properties`()
@Test
fun `service constants are correct`()
}✅ Both apps compile and run without errors
✅ Location collected every 2-3 minute in background
✅ Service survives reboot and system kills
✅ Data encrypted with KeyStore
✅ Commands sent and responses received reliably
✅ 80%+ test coverage
✅ CI/CD pipeline runs successfully
✅ Clean Architecture properly implemented
✅ Comprehensive documentation provided
✅ Git Flow followed with clear commits
✅ Error handling and recovery logic
✅ Analytics and performance monitoring